It appears the little 250ci I-6 Chevy in my '46 2-ton has seen it's better days. When I first transplanted it in, it ran great, save for what I think is a wrist pin tapping at any speed above idle*. But the last few times I've had it out, I've had a bear of a time keeping it tuned. Can never seem to dial in the idle to where it stays the same from one day to the next and the timing advance curve acting stupid. Now today I take the truck out and it stalls every time I let off the gas pedal. Going down the road it seems to run great until I put a good load on the engine. That's where the spark rattle starts.
So I limp it to my mom's, back it in the garage and attempt to turn the idle speed screw in to gain some more idle RPM's since it kept dying. It's turned in as far as it will go and the engine couldn't be running 350 rpm's!
And that's when I notice the oil. On top of the valve cover where the oil fill is. I go to the passenger side of the engine and the oil is bubbling out the hole for the dipstick tube. I pull the PCV valve and stick my finger on it. No vacuum. Not a bit. So I pull the line off the vacuum advance. Nothing. The big line directly off the intake manifold for the power brakes? Barely noticeable. I look for any flammable squirty stuff to spray around the intake manifold to check for a vacuum leak but mom was fresh out. Crap.
So now I'm thinking the engine sucked in the intake manifold gasket. That's the only explanation I can come up with for the zero vacuum condition at all the ports, but it doesn't explain the crankcase pressure.
Any thoughts anyone?
*Wrist pin "diagnosis": Top-rear of engine. Rhythmic tapping at any engine speed above idle. Noise increases dramatically on decel, especially when coasting against engine downhill or down shifting. Cannot adjust the noise away buy adjusting valves. All push rods are straight. Thought possibly collapsed lifter so replaced them all. No change. 40 psi oil pressure.
Last edited by Dieseldude03; 09/13/2013 2:21 PM.
